This paper presents the effects of simulated dust pollution on the breakdown characteristics of protective gaps subjected to standard switching impulses (250/2500 μs) of both polarities. Hemispherical and square cut rod gaps were employed and their performance was compared in a gap spacing varying from 5 cm to 120 cm. It was found that dust pollution either reduces the 50% breakdown voltage or increases it, depending upon the gap spacing. Formation of a stable dust particle film on the cathode was found to control these irregularities in breakdown parameters. It was also found that square cut rod gaps display immunity toward dust pollution under positive switching impulses and are therefore best suited for applications in terrains where dust storms are common.